The present invention generally relates to the control circuits of film or tape transport machines, and more particularly to a power interlock circuit for preventing the main power from being turned off while the high speed forward or reverse motors of the film or tape machine are running.
In microfilm readers or audio or video tape transports or similar devices, there is a problem when the film or tape is being moved in either the forward or reverse direction by the high speed motors of the transport and the operator turns off the power switch. Due to the inertia of the high speed motors and reels and a lack of power to operate the brake, overrun of the film or tape inevitably results causing great problems inside the machine and many jam ups. At the very least, the film or tape might have to be rewound by hand and often serious damage results to the film or tape and occasionally to the transport mechanism.